Report on Rainwater Harvesting System for Shantiniketan Layout, Arekere, Bangalore

Report on rainwater harvesting system for Shantiniketan Layout, Arekere, Bangalore – revised

Submitted by

Biome Environmental Solutions Pvt Ltd, (Earlier Rainwater Club) No. 15, 1st Block, 1st Main, BEL Layout, Vidyaranyapura Bangalore – 560 097 www.rainwaterclub.org www.biome-solutions.com

TABLE OF CONTENTS No. Details Page no. 1.0 Client and document details 3 2.0 Overview 3 3.0 Land area and land use 4 4.0 Water supply and consumption 5 5.0 Rainfall and potential runoff 10 6.0 Rainwater harvesting – existing system 17 7.0 Reference images 18 8.0 Resources 20 9.0 Further engagement with Biome 21 10.0 Recommendations for RWH and groundwater recharge 21 List of tables No. Details Page no. Table 1 Land use distribution 4 Table 2 Borewell details 6 Table 3 Open well details 7 Table 4 Population calculation for the layout 9 Table 5 Water demand calculation 10 Table 6 Average rainfall received by Bangalore 10 Table 7 Potential runoff for RWH 11 Table 8 Annual demand vs. rooftop runoff 11 Table 9 Road / paved area runoff details for 20 mm rain 13 Table 10 Calculation for 3 x 20 recharge wells for roads/paved areas 13 Table 11 Open / unpaved area runoff details for public parks 14 Table 12 Calculation for 3 x 20 recharge wells for public parks 14 Table 13 Calculation for 6 x 30 recharge wells for public parks 14 Table 14 Open / unpaved area runoff details for temple parks 15 Table 15 Calculation for 3 x 20 recharge well for Premkala Gelli park 15 Table 16 Calculation for 6 x 30 recharge well for Sai Baba Temple 15 Table 17 Calculation for 3 x 20 recharge wells for the vacant plots 15 Table 18 Calculation for 3 x 20 recharge wells on BWSSB norms 16 List of figures No. Details Page no. Figure 1 Map of Shantiniketan layout 3 Figure 2 Property break-up in the layout 4 Figure 3 Land area and land use 4 Figure 4 Locations of open wells, recharge wells and borewells 5 Figure 5 Images of borewells, OHT and sumps 6 Figure 6 Images of open wells 8 Figure 7 Images of recharge wells 9 Figure 8 Proposed recharge well locations 16 Figure 9 Current state of some of the drains 17 Figure 10 Nala running through layout 18

1.0 Client and document details

Client name Shantiniketan Residents Welfare Association

Client contact details [email protected], 9980906667

Document date September 27, 2019

Document version Revised

2.0 Overview Biome was invited to visit Shantiniketan Layout, Arekere by the SRWA to understand its water situation and help evolve a way forward for the water resources management at the layout. The overall objective of Biome’s engagement is to develop a sustainable rainwater harvesting strategy for the common areas and suggest other water conservation measures that can be adopted by the community. Shantiniketan Layout is a BDA sanctioned layout that was developed in 1992. The total layout area is about 47 acres and is a mix of residential and commercial buildings, parks and other CA (civic amenities). The residential properties are a combination of independent houses, and small and mid-sized apartments. There are some temples located in the park / CA areas. There are 495 plots with houses, 48 plots with apartments, 115 vacant plots and 21 plots with commercial buildings.

Figure 1: Map of Shantiniketan layout The figure below shows the break up of the types of properties in the layout – most of them are residential (92.84 %) and very few are commercial.

Figure 2: Property break-up in the layout

3.0 Land area and land use The land use distribution shows that 41% area is rooftop, followed by unpaved / open area of 32% and paved / road area of 27%. Land use distribution Area Type of area Sqm Sft Acres % Total layout area 189011 2034514 47 100% Open spaces 61117 657869 15 32% Roads 50836 547199 13 27% Roof area 77058 829447 19 41%

Table 1: Land use distribution

Figure 3: Land area and land use

4.0 Water supply and consumption The main sources of water supply are Cauvery water from BWSSB, which supplies water twice a week to the entire layout, and borewells, the details of which are given below. About one-third of the houses in the layout have their own borewells.

Figure 4: Locations of open wells, recharge wells and borewells

4.1 Borewells Borewell details Borewell Year of Depth Casing Description name digging (ft) (ft) BW1 700 60 Main source of supply to entire layout. It supplies water twice a week - once to half the layout and once to the remaining half. Overall, it serves around 500 plots. On an average, it needs to be pumped for two days to fill up the sump of 5.55 lakh litres and one day to fill up the overhead tank of 1.8 lakh litres. The submersible pump motor is located about 250 meters away, near the UG sump / OHT BW2 450 20 This borewell is located in the premises of the Sai Baba temple. The yield has reduced in recent times BW3 The machinery got damaged while digging and re- digging was not attempted. Filled with rocks BW4 300 15 This borewell is located in Shantiniketan Tank Park and is used for watering the park. Yield reduces after 1 hour BW5 Non-yielding borewell located near Shantiniketan Tank Park BW6 550 Located in CA Site Park which takes care of the gardening needs of the park 5

BW7 Located in Vyasa Bank Colony Park, which takes care of the gardening needs of the park. Presently, the motor is under repair BW8 Located near Family Park BW9 Camera inspection has been done and the report needs to be seen. This borewell is connected to a 14000-litre sump. BW10 Non-yielding borewell Table 2: Borewell details

Figure 5: Images of borewells, OHT and sumps

4.2 Open wells The Biome team was able to inspect seven open wells. There are a few more wells, yet to be located and inspected.

Open well details Open Year of Diameter Depth Static Remarks well digging (ft) (ft) water name level (ft) W1 2' 9" 18 There seems to be seepage of (pvt) sewage water into the well. The water is used for cleaning, dish washing and clothes washing. Cauvery water is used for cooking, drinking and bathing. W2 2002 4 24 10 Water is used for the gardening (park) needs of the park in Vasavi Temple W3 4 18 16 First open well in Family Park. (park) Water is used for gardening needs of the park W4 4 26 24 Second open well in Family Park. (park) Has very little water now W5 3 18 This well is used for recharging (pvt) rooftop rainwater. Its water is not used for any purpose, since it is very dirty and sewage water seems to be seeping into the well W6 2003 3 18 8 Water is used for cleaning, car (pvt) washing and flushing toilets W7 3 12 6 Water is used for all uses except (pvt) drinking and cooking Table 3: Open well details

Figure 6: Images of open wells

4.3 Recharge wells There are a few recharge wells made by the BBMP in the parks, measuring around 5 ft deep. But none of them are being maintained. They are filled with debris or used for composting organic waste. Their inlets are blocked or completely closed.

Figure 7: Images of recharge wells

4.4 Water demand The following assumptions have been made for the purposes of calculation: ● 5 members per residential plot and 2 houses in a plot ● 100 footfalls per preschool ● For smaller commercial properties, footfall of 500 per commercial space

The following is a conservative estimate. It was not possible to obtain details of the total supply to the entire layout, as there are multiple sources, which vary across the different properties, and centralized collation of data is not possible. To calculate the water demand for the entire layout, the following assumptions have been made: ● National Town Planning norms have been used, which give the figure of 150 LPCD for metro cities and towns with UGD ● For calculating floating population, commercial properties and institutions have been considered ● For calculating demand of floating population, 50 LPCD has been considered

No. of persons in Total Type of property No. of property units each property unit population Preschool (floating) 7 100 700 Restaurant (floating) 2 500 1000 Shop (floating) 9 500 4500 Office (floating) 2 500 1000 Residential house 495 10 4950 Apartment building 23 60 1380 Total 13530

Table 4: Population calculation for the layout

The total population (residents and floating population) is found to be 13530. The residents number 6330 and the floating population is 7200.

The following table gives the approximate water demand of Shantiniketan layout:

Total water Type of No. of Water usage per person per demand per population people day considered (litres) day (KLD) Residential 6330 150 litres per person 950 Floating population 7200 50 litres per person 360 Total 1310 Table 5: Water demand calculation

The daily water demand of Shantiniketan layout is 1310 KL (kilolitres). The monthly demand is 39285 KL and the annual demand is 477968 KL (477.9 million litres).

5.0 Rainfall and potential runoff The average rainfall that Bangalore receives has been recorded as 970-975 mm with the average number of rainy days as 60. The table below provides the distribution of rainfall over the months of the year.

Average rainfall Average rainy Month (mm) days Jan 1.8 0.2 Feb 7.9 0.5 Mar 7 0.8 Apr 40 3 May 110.2 6.9 Jun 89.1 6 Jul 108.9 7.4 Aug 142.5 10 Sept 241 10.3 Oct 154.5 7.9 Nov 54.1 3.9 Dec 17.5 1.6 Total 974.5 58.5 Table 6: Average rainfall received by Bangalore The total rain that falls on an area is called the rainfall endowment of that area. Not all of this rain can be harvested, or is visible as runoff. The percentage of runoff depends on the surface that the rain falls on. The greater the percentage of paved / built up area, the more runoff – this can be up to 90% of the rainfall endowment. The runoffs from the various surfaces of the layout for annual rainfall, 10 mm rain, mild rain (20 mm) and heavy rain (60 mm) are given in the table below.

The area of the vacant plots and setbacks have not been taken into consideration: Type of Area Runoff Annual Runoff Runoff Runoff Contri catchment (sqm) coeffici runoff at at 10 at 20 at 60 bution ent 974.5 mm mm mm to total mm rain rain rain rain runoff (KL) (KL) (KL) (KL) Rooftop area 77058 0.9 67583 694 1387 4161 59 % Paved areas 50836 0.7 34678 356 712 2135 30 % (roads) Open areas 23889 0.3 6984 72 143 430 6 % (parks / CA) Open areas 19963 0.3 5836 6 60 359 5 % (115 vacant plots) Open areas 17266 (setbacks) TOTAL 189011 115081 1181 2362 7086 100 % Table 7: Potential runoff for RWH From the table above it can be seen that the maximum runoff is from the rooftops, whose contribution to the total runoff is 59 %. Runoff from paved areas contributes 30 % to the total. Total daily water demand 1310 KLD Total annual water demand 477968 KL/year Total annual rooftop runoff 67583 KL/year Total demand met by rooftop runoff 14 % Table 8: Annual demand vs. rooftop runoff

5.1 Rooftop runoff It is possible to harvest around 67583 KL of water from the rooftops of the houses. This can meet around 14 % of the current annual consumption of 477968 KL; provided rainfall is normal and adequate storage is created. The rest of the water demand needs to be met by either BWSSB water supply and/or groundwater. In other words, at some level, the layout depends on groundwater making it a critical necessity to do groundwater recharge. It is imperative to harvest as much rainwater as possible since at least 14% of the total water demand can be met through it. If all the paved and open area runoff is captured and used, it can meet 9% of the total demand.

5.2 Roads / paved area runoff The paved and open area runoff should be used for groundwater recharge. This will help raise the groundwater table. For this, structures called recharge wells should be dug. We recommend that recharge wells of size 6 ft x 30 ft be dug in parks and common areas, and recharge wells of size 3 ft x 20 ft be dug in the stormwater drains. Rainwater harvesting potential for road / paved area runoff @ 20 mm rainfall (maintained by SRWA) Runoff Recharge from 20 volume of Number of Road Area Runoff mm rain 3'x20' well wells S No description (sqm) coeff (KL) (KL) required 1 Road 1 690 0.70 10 6 2 2 Road 2 630 0.70 9 6 1 3 Road 3 608 0.70 9 6 1 4 Road 3a 410 0.70 6 6 1 5 Road 4 1340 0.70 19 6 3 6 Road 5 628 0.70 9 6 1 7 Road 6 1368 0.70 19 6 3 8 Road 6A 3212 0.70 45 6 7 9 Road 6B 1880 0.70 26 6 4 10 Road 6C 892 0.70 12 6 2 11 Road 7 602 0.70 8 6 1 12 Road 8 6018 0.70 84 6 14 13 Road 9 645 0.70 9 6 2 14 Road 10 275 0.70 4 6 1 15 Road 11 1647 0.70 23 6 4 16 2nd Cross road 793 0.70 11 6 2 17 3rd Cross road 710 0.70 10 6 2 18 3rd B Cross rd 685 0.70 10 6 2 19 4th Cross road 356 0.70 5 6 1 20 1st Main road 596 0.70 8 6 1 21 2nd Main road 545 0.70 8 6 1 22 3rd Main road 692 0.70 10 6 2 23 4th Main road 799 0.70 11 6 2 24 5th Main road 1373 0.70 19 6 3 25 6th Main road 441 0.70 6 6 1 26 7th Main road 688 0.70 10 6 2 27 8th Main road 579 0.70 8 6 1 28 9th Main road 669 0.70 9 6 2 29 10th Main road 642 0.70 9 6 1 30 11th Main road 787 0.70 11 6 2 31 12th Main road 919 0.70 13 6 2 32 13th Main road 838 0.70 12 6 2 33 14th Main road 805 0.70 11 6 2 12

34 15th Main road 896 0.70 13 6 2 35 Sai Baba Temple 4110 0.70 road 58 6 10 36 A Main road 2854 0.70 40 6 7 37 B Main road 626 0.70 9 6 1 38 C Main road 695 0.70 10 6 2 39 D Main road 688 0.70 10 6 2 40 E Main road 413 0.70 6 6 1 41 F Main road 764 0.70 11 6 2 42 G Main road 672 0.70 9 6 2 43 H Main road 489 0.70 7 6 1 44 I Main road 605 0.70 8 6 1 45 J Main road 622 0.70 9 6 1 46 K Main road 685 0.70 10 6 2 47 4th Cross road 693 0.70 10 6 2 48 5th Cross road 664 0.70 9 6 2 49 6th Cross road 753 0.70 11 6 2 50 6th A Cross road 841 0.70 12 6 2 Total 50836 712 6 119 Table 9: Road / paved area runoff details for 20 mm rain

Diameter 3 ft Depth 20 ft Static water volume 4 KL Recharge volume 6 KL Surface runoff generated in 20 mm rain 712 KL Total number of recharge wells 119 No. Table 10: Calculation for 3 x 20 recharge wells for 20 mm rain

For effectively recharging the runoff from the paved areas and roads in a 20 mm rain, the layout needs 119 recharge wells of 3 ft diameter and 20 ft depth.

5.3 Public parks runoff Rainwater harvesting potential for open / unpaved area runoff @ 20 mm rainfall for public parks (maintained by BBMP) Runoff from Recharge Number S Area Runoff 20 mm rain volume of of wells No Park description (sqm) coeff (KL) 3'x20' well (KL) required 1 Playground 01 746 0.30 4 6 1 2 Family Park 1022 0.30 6 6 1 3 Children’s Park 01 457 0.30 3 6 1 4 Playground 02 940 0.30 6 6 1 5 Vysya Bank Colony Park 860 0.30 5 6 1

6 CA site park 1074 0.30 6 6 1 7 Children’s Park 02 1392 0.30 8 6 1 Total 6491 39 7 Recharge volume of 6'x30' well (KL) 8 Playground 6196 0.30 37 36 1 9 Shantiniketan Tank 5851 0.30 Park 35 36 1 Total 12046 72 2 Table 11: Open / unpaved area runoff details for 20 mm Rain for public parks

Diameter 3 ft Depth 20 ft Static water volume 4 KL Recharge volume 6 KL Surface runoff generated in 20 mm rain 39 KL Total number of recharge wells 7 No. Table 12: Calculation for 3 x 20 ft recharge wells for public parks 1-7

Diameter 6 ft Depth 30 ft Static water volume 24.0 KL Recharge volume 36 KL Surface runoff generated in 20 mm rain 72 KL Total number of recharge wells 2 No. Table 13: Calculation for 6 x 30 ft recharge wells for public parks 8-9

For effectively recharging the runoff from the public parks in a 20 mm rain, the layout needs 1. 7 recharge wells of 3 ft diameter and 20 ft depth for the first 7 parks, and 2. 2 recharge wells of 6 ft diameter and 30 ft depth for parks 8 and 9

5.4 Temple parks runoff Rainwater harvesting potential for open / unpaved area runoff @ 20 mm rainfall for temple parks Runoff from Recharge volume Number S Area Runoff 20 mm rain for 3'x20' well of wells No Park description (sqm) coeff (KL) (KL) required 10 Premkala Gelli Park 1445 0.30 9 6 1 Recharge volume for 6'x30' well (KL) 11 Sai Baba Temple 3908 0.30 23 36 1 14

Park Table 14: Open / unpaved area runoff for temple parks

Diameter 3 ft Depth 20 ft Static water volume 4 KL Recharge volume 6 KL Surface runoff generated in 20 mm rain 9 KL Total number of recharge wells 1 No. Table 15: Calculation for 3 x 20 recharge well for Premkala Gelli Park

Diameter 6 ft Depth 30 ft Static water volume 24.0 KL Recharge volume 36 KL Surface runoff generated in 20 mm rain 23 KL Total number of recharge wells 1 No. Table 16: Calculation for 6 x 30 recharge well for Sai Baba Temple Park

For effectively recharging the runoff from the temple park areas in a 20 mm rain, the layout needs 1. 1 recharge well of 3 ft diameter and 20 ft depth for Premkala Gelli Park, and 2. 1 recharge well of 6 ft diameter and 30 ft depth for Sai Baba Temple Park

5.5 Vacant plots runoff For open areas of vacant plots considering runoff generated at 20 mm rainfall Diameter 3 ft Depth 20 ft Static water volume 4.0 KL Recharge volume 6 KL Surface runoff generated at 20 mm rain 120 KL Total number of recharge wells 20 No. Table 17: Calculation for 3 x 20 recharge wells for the vacant plots

There are 115 vacant plots for which 20 recharge wells of 3 ft diameter and 20 ft depth are required. So, for every 5-6 plots, 1 recharge well can be dug, according to the space available and the runoff direction.

Figure 8: Proposed recharge well locations

As per BWSSB’s RWH regulations: ● For every non-rooftop area: 10 litres of runoff per sqm (lpsqm) of non- rooftop area should be captured and used for groundwater recharge (10 mm rain) ● For every rooftop area: 20 litres of runoff per sqm of rooftop area should be captured and used for storage or groundwater recharge (20 mm rain)

Runoff generated at 10 mm rain as per BWSSB norms for paved & open areas Diameter 3 ft Depth 20 ft Static water volume 4.0 KL Recharge volume 6 KL Surface runoff generated at 10 mm 947 KL Total number of recharge wells 158 No. Table 18: Calculation for 3 x 20 recharge wells according to BWSSB norms

For road / paved areas, open areas in parks / CA sites and runoff from vacant plots, 158 recharge wells of 3 ft diameter and 20 ft depth are required as per the BWSSB norms.

6.0 Rainwater harvesting - existing system At present, there is no information on the number of houses with rainwater harvesting in place. Except for a few recharge wells in the parks, which are not effective, there are no recharge wells in the layout. Also, the drains are blocked in many places.

Figure 9: Current state of some of the drains There is a nala running through the middle of the layout from west to east, towards which the roads slope from both the north and south parts of the layout. This nala runs from the Arekere Lake and turns south after exiting Shantiniketan layout and runs towards Hulimavu Lake. It is covered and it was not possible to observe whether it contained water, or whether there was any sewage entering it. The nala is indicated by the purple line in the figure below.

Figure 10: Nala running through the layout

7.0 Reference images

1. In-drain filter / inlet and outlet pipes of recharge wells:

2. Recharge wells:

3. Bangalore’s geology:

8.0 Resources Recharge Well Primer with contact details of well diggers: http://bengaluru.urbanwaters.in/recharge-well-primer-398 Rainwater Harvesting Regulation for Bangalore: http://bengaluru.urbanwaters.in/wp- content/uploads/sites/3/2018/09/Rainwater-Harvesting-Regulations-1.pdf 20

Open Well Primer: http://bengaluru.urbanwaters.in/open-wells-60

9.0 Further engagement with Biome Based on these recommendations if the client wishes to engage with Biome further, the scope of engagement would include the following: 9.1 Detailed design for recharge wells including filtration, etc. and location of all recharge wells 9.2 Recommendation of contractors for well digging and supervision during implementation of two pilot recharge wells in the layout. Biome will supervise the implementation strictly for adherence to the design, not for project management 9.3 Slug tests on pilot recharge wells

10.0 Recommendations for rainwater harvesting and groundwater recharge (These are being detailed at the end of the report on the client’s request) 10.1 General recommendations Conduct slug tests on the existing recharge wells, after cleaning and deepening them to at least 20 ft. A slug test is done by filling the recharge well with a known quantity of water and observing the time taken for the water to percolate completely. This test is done to understand the recharge rate of the shallow aquifer. Based on the results of the above tests, the depth and distribution of the proposed new recharge wells may need to be altered. 10.2 Actions to be taken by the layout residents 10.2.1 Rainwater harvesting systems need to be installed in all the existing houses and any upcoming houses / apartments. They can either implement storage and reuse of rooftop rainwater or groundwater recharge 10.2.2 Metering of all borewells and individual houses / apartments – this should be taken up on an immediate basis, and a regular record of the readings maintained. 10.2.3 RO reject water should be collected and used to wash dishes, mop floors, water the garden / potted plants, wash the car, wash clothes, etc 10.2.4 Old and new homes should be encouraged to use water efficient fixtures - like aerators and low flow taps, flushes, showers, etc

10.2.5 All houses - old and new- should implement grey water treatment and reuse systems 10.2.6 There are 115 vacant plots for which 20 wells of 3 ft diameter and 20 ft depth are required. So, for every 5-6 plots, 1 recharge well can be dug, according to the space available and the direction of flow of runoff For open areas of vacant plots considering runoff generated at 20 mm rainfall Diameter 3 ft Depth 20 ft Static water volume 4.0 KL Recharge volume 6 KL Surface runoff generated at 20 mm rain 120 KL Total number of recharge wells 20 No.

10.3 Actions to be taken by SRWA 10.3.1 For effectively recharging the runoff from the paved / road areas in a 20 mm rain, the layout needs 119 recharge wells of 3 ft diameter x 20 ft depth. The cost of a single recharge well of 3 ft diameter x 20 ft depth varies between 30,000/- to 45,000/- Diameter 3 ft Depth 20 ft Static water volume 4 KL Recharge volume 6 KL Surface runoff generated in 20 mm rain 712 KL Total number of recharge wells 119 No. 10.3.2 The recharge wells once done, need to be desilted once in one or two years, to ensure effective recharge. Also, the stormwater drains (roadside drains) need to be cleaned and maintained regularly, especially before the start of the monsoon. Any leakages to the nala / rajakaluve need to be plugged. 10.3.3 Borewell recharge: As per the data given by SRWA, there are 3 dry borewells in the layout and following 2 options can be tried for borewell recharge: Option 1: Direct recharge with runoff from the nearest rooftop to the borewell In this method, the classic approach is to dig a pit around the borewell – the depth of this pit can vary from 8 to 20 ft. At the bottom of this pit, the borewell casing is punched with small holes or slits, and is wrapped tightly with several layers of fine mesh. The pit is then filled with several layers of graded gravel (jelly stones) and sand, or sand and charcoal. This serves to filter the water that flows into the pit before it enters the borewell through the punched holes. Rainfall runoff water from the nearest rooftop ONLY is channelled into this pit, 22

and thence enters the borewell. Since the water is directly entering the borewell, in order to ensure water quality, only clean rooftop surfaces are used for this option. Instead of digging a pit, the rooftop water can also be passed through a surface filter (sized according the rule ‘1 litre per sqm of rooftop area’) and piped directly into the borewell without digging the pit or punching holes in the casing. This will work out less expensive, and also reduce the chances of fine silt / clay particles entering the borewell and clogging the water sources.

Option 2: Conversion of one dry borewell into a shallow borewell with a recharge well upstream

This is an experiment to test the efficacy of indirect recharge - it is based on the experience of Rainbow Drive layout (whose shallow borewells have revived after some years of shallow aquifer recharge through 200+ recharge wells) and the

observation of farmers near Bettakote lake converting their deep borewells into shallow ones (since the lake started holding water all year round and recharged the shallow aquifer around it). In this experiment, a deep borewell that has been dry for some years will be rendered shallow (100 - 150 ft) by blocking it at the appropriate depth, and cutting slots in its casing above this point. It is assumed that as rainwater percolates from the recharge well upstream of this borewell, it will pass into the borewell through the slots in its casing and accumulate within it, instead of disappearing into its depths. However, this is possible ONLY when a source at shallower depths is encountered inside the borewell through camera inspection. Please also note that this is an experiment.

10.4 Actions to be taken by public parks / BBMP: 10.4.1 For effectively recharging the runoff from the public park areas in a 20 mm rain, the layout needs 7 recharge wells of 3 ft diameter x 20 ft depth and 2 recharge wells of 6 ft diameter x 30 ft depth 10.4.2 As seen in some of existing recharge wells in the public parks, the recharge well depth of 5 ft is not going to help much - the depth of the recharge wells needs to be at least 20 ft for effective recharge to occur 10.4.3 The cost of a single recharge well of 3 ft diameter x 20 ft depth varies between Rs 30,000/- to 45,000/- and the cost of a 6 ft diameter x 30 ft depth recharge well is around Rs 1,00,000/- to 1,25,000/- Rainwater harvesting potential for open / unpaved area runoff @ 20 mm rainfall for public parks (maintained by BBMP) Runoff from Recharge volume Number S Area Runoff 20 mm rain of 3'x20' well of wells No Park description (sqm) coeff (KL) (KL) required 1 Playground 01 746 0.30 4 6 1 2 Family Park 1022 0.30 6 6 1 3 Children’s Park 01 457 0.30 3 6 1 4 Playground 02 940 0.30 6 6 1 5 Vysya Bank Colony Park 860 0.30 5 6 1 6 CA site park 1074 0.30 6 6 1 7 Children’s Park 02 1392 0.30 8 6 1 Total 6491 39 7 Recharge volume of 6'x30' well (KL) 8 Playground 6196 0.30 37 36 1 9 Shantiniketan 5851 0.30 Tank Park 35 36 1 Total 12046 72 2

10.4.4 There is a nala running in the middle of layout below a 12 m wide road, which connects Arekere Lake upstream and Hulimavu Lake downstream. The quantity and quality of water flowing through this nala is not known and needs further exploration. It is suggested that SRWA anchor the engagement with BBMP / BWSSB/ KSPCB to check the feasibility of reusing the water flowing in the nala within the layout. Biome will support SRWA during the conversation with relevant authorities, to explore taking this idea forward. 10.5 Actions to be taken by temple parks: 10.5.1 For effectively recharging the runoff from the temple park areas in a 20 mm rain, the layout needs 1 recharge well of 3 ft diameter x 20 ft depth and 1 recharge well of 6 ft diameter x 30 ft depth 10.5.2 As seen in some of existing recharge wells in the temple parks, the recharge well depth of 5 ft is not going to help much - the depth of the recharge wells needs to be at least 20 ft for effective recharge 10.5.3 The cost of a single recharge well of 3 ft diameter x 20 ft depth varies between Rs 30,000/- to 45,000/- and cost of a recharge well of 6 ft diameter x 30 ft depth is around Rs 1,00,000/- to 1.25,000/- Rainwater harvesting potential for open / unpaved area runoff @ 20 mm rainfall for Temple Parks Runoff Recharge from 20 volume for Number Area Runoff mm rain 3'x20' well of wells S No Park description (sqm) coeff (KL) (KL) required 10 Premkala Gelli Park 1445 0.30 9 6 1 Recharge volume for 6'x30' well (KL) 11 Sai Baba Temple Park 3908 0.30 23 36 1

10.6 Collective actions: Out of the seven open wells inspected, there is water at a depth of around 10 ft in six of them. Hence, open wells can be dug as sources of water in the layout. This could be done initially in the parks and subsequently in individual houses by interested residents. If done along with recharge wells, it will ensure that the open wells will always have water, and this will reduce the current dependence on Cauvery water and borewell water to a significant extent.